A Link Between Air Pollution and Adolescent ADHD

Certain pollutants common to urban areas could be harming the brains of unborn children, according to new research.

Researchers from Columbia University and elsewhere have found a possible link between air pollution and adolescent ADHD. According to the report, published today in the journal PLOS ONE, pregnant women from New York City exposed to certain air pollutants were more likely to birth a child with ADHD. The pollutants —polycyclic aromatic hydrocarbons (PAH)—are released into the atmosphere through the burning of coal, tobacco, and petrol.

The research team monitored 233 nonsmoking women living in Harlem, Washington Heights, and the Bronx. The women and their household pollutant levels were monitored from the time of pregnancy until their children reached the age of 9. Those living in highly polluted areas were five times as likely to give birth to a child that developed ADHD during the course of the study. (The researchers controlled a number of factors, including; sex of the child, the child's ethnicity, the mother's education level, maternal ADHD symptoms, and quality of home caretaking environment).

"This study suggests that exposure to PAH encountered in New York City air may play a role in childhood ADHD," explains Dr. Frederica Perera, the report's lead author.

This graph shows the presence of pyrene, a PAH chemical, in the systems of NYC children. Between 2001 and 2012, researchers found young New Yorkers more exposed to the toxin during winter months, when households burn coal for heat. (Environmental Research)

This potential correlation is of increasing concern because other research shows PAH toxins resurfacing in certain urban households (see graphs above). A similar study from this year found an uptick in PAH exposure among New York City children between 2005 and 2012. Not surprisingly, household air pollutants were more prevalent during winter months as people burned coal to heat their homes. Yet, coal burning is on the decline in most developed urban centers; the most commonly emitted PAH toxins "have decreased substantially in the last 30 years," according to the WHO.

This graph shows the suspected presence of napthalene, another PAH chemical, in the systems of young New Yorkers between 2001 and 2012. (Environmental Research)

Given that household coal consumption is decreasing, along with the number of heavy smokers in America, individual behavior is evidently not fueling this potential link between air pollution and ADHD. Instead, the focus may need to be on broader urban policies that might be harming the brains of unborn children.

Building homes along the borders of highways, for example. Or further regulating the volume of coal burned by American power plants (they're burning more coal these days, by the way). Pushing for more sustainable public transportation is another obvious choice.

Coal burning, one way to release PAH toxins, is on the rise. (U.S. Energy Information Administration)

CityLab previously reported that green areas have been linked to fuller pregnancies and healthier babies. Could these green, less polluted areas also mitigate the ubiquity of adolescent ADHD? If so, what a breath of fresh air.